There are many ways to share image information over the internet but these tools are generally driven by technology rather than led by users. In particular many people use dry erase whiteboards and similar surfaces in both the work and home environments but, as yet, there is no simple and effective way to capture or share information on such a whiteboard. Typically a user wanting to capture or share information will take a photograph with a mobile phone and then email this, but such photographs are often of poor quality and difficult to read, frequently exhibiting distortions and large regions of reflective light beneath which it is difficult to discern the content. It is possible to purchase whiteboards with a built in scanner but these are cumbersome and expensive devices and are often more suited to printing than sharing information.
A whiteboard image capture system has been described by Microsoft Corporation in, ‘Why Take Notes? Use the Whiteboard Capture System’, L. He et al, Microsoft Research Technical Report: MSR-TR-2002-89. This describes a colour-based approach in which writing is distinguished from the background whiteboard by comparison with the whiteboard colour. However this approach suffers from some serious defects. Although the human eye exhibits colour constancy, to a camera the colour and intensity of the whiteboard varies substantially with ambient light level and quality. Furthermore the Microsoft system employs a camera viewing the whiteboard essentially normal to the whiteboard whereas for a practical system it is desirable to be able to view the whiteboard from an acute angle. However when viewed from an acute angle the whiteboard surface is highly reflective, and this can result in a substantial degree of specular reflection, and “coloured shadows” from the user, which the colour-based approach of the Microsoft system does not handle well.
Accordingly there is a need for improved approaches.